The court also heard of a 68-page document that lists the names of those who have asked Glenn Mulcaire, the private investigator jailed for phone hacking, to intercept voicemails.

The document, based on his notes, has been handed to lawyers acting on behalf of phone – hacking claimants by the Metropolitan Police but its contents remain confidential to protect the criminal investigation.

Mark Lewis, the lawyer leading the response to the scandal, described the email archive as "amazing".

"This calls into serious doubt the first police investigation under the former assistant commissioner, Andy Hayman, who described his efforts as 'not leaving a stone unturned',” Mr Lewis, who is acting for several victims, told The Independent.

He urged Lord Leveson, who is leading the judicial inquiry into phone hacking, to establish why several police investigations were “so inadequate”.

The scandal has left an extraordinary mark on Britain’s media and political landscape as well as on the News Corporation empire founded by Rupert Murdoch.

A total of 16 people have been arrested on suspicion of phone hacking at the axed tabloid.

A number of people have resigned including Scotland Yard Commissioner Sir Paul Stephenson, his Assistant Commissioner John Yates and two trusted Murdoch executives – former NI chief executive Rebekah Brooks and chairman Les Hinton.

Last week NI confirmed it was in advanced settlement talks with the parents of murdered schoolgirl Milly Dowler over police claims that the 13-year-old's mobile phone was hacked after she went missing.

A total package of £3 million is being finalised, including a £1 million personal donation from Rupert Murdoch to charity.

This week it emerged that two former senior NoTW staffers, Neville Thurlbeck, its 50 year-old former chief reporter and former news editor Ian Edmondson, 42, have taken the company to an employment tribunal, claiming unfair dismissal.

Meanwhile, James Murdoch, who oversees News International, is to face further questions from MPs investigating the phone hacking scandal over claims that he gave misleading evidence about his knowledge of the illegal practice.

On Wednesday News International denied that access to the emails was in response to a compulsory "disclosure" order.

"We continue to co-operate fully with the Metropolitan Police in its investigations into phone hacking and police payments,” a spokeswoman said. The company also said it would “vigorously contest” the employment tribunal cases.